Steam generator



sept. 22, T1942.

4. BLIZARD STEAM GENERATOR Filed, Nov.., 2 5, 1938 .lez /7 INVENTOR .EH/v, BL /Z/Wo.

ATTORNEY Patented Sept. 22, 1942 STEAM GENERATOR John Blizard, Garden City, N. Y., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application November 25, 1938, Serial No. 242,215

. 6 claims. (01.1224478) This invention relates to the generation and superheating of vapors and more particularly pertains to steam generators and superheaters. The invention provides a combination of a forced circulation boiler and a natural circulation boiler with meansfor controlling the temperature or the degree of superheat, of the steam.

The invention will be understood from the following description considered in connectionwith the accompanying drawing, the single figure of which illustrates diagrammatically a steam generator embodying the invention.

Referring to the drawing, reference character l designates the setting of a steam generator which encloses a forced circulation steam generating section at its right hand end as viewed in the drawing, a natural circulation steam generating section at its left hand end, and a superheating section inthe forced circulation section.

Feed water is supplied to the generator through line VII to a feed pump I2 which delivers it to an economizer I3 in a flue I4, the inlet of which connects with' the setting at a point between the forced and natural circulation sections of the generator. From the economizer the water flows through line I 5 to a header I6 at the upper right hand end of the generator and through a plurality of rows of steam generating tubes I1, the inlet end portions of which, as shown, are looped to define the major portion of a furnace chamber I8 which is fired by a plurality of fuel burners I9 adapted to burn pulverized coal, oil, or gas, or a combination of these fuels. One or more burners I9 may be used to re the furnace I8. Intermediate the chamber I8 and the flue I4, the steam generating tubes are formed into a plurality of return bend loops, and the water flowing therethrough and the steam generated therein is delivered to a steam and water drum 2|] of the natural circulation boiler section. A bank of steam generating tubes 2I connects the upper drum and the lower drum 22 which is shown as located somewhat to the right of a position immediately below the upper drum 20, but it may be disposed in other positions if desired. Tubes 23 connecting the upper and lower drums 20 and 22 define with the bank of tubes 2|, a furnace chamber 24 which is fired by a plurality of fuel burners 25 like, or similar to, the burners I9.- One or more burners 25 may be used.

Steam in the drum 20 is conducted through line 26 to the inlet header 21 of a superheater 28 which is disposed in the tubebank I1 between the furnace I8 and the flue I4. The superheated line 30 to the point of use. The superheater may be located in any suitable position in the forced circulation boiler.

The natural circulation section of the generator will always be in use during operation of the generator. To maintain a constant, or substantially constant, level of water in the drum 20, water must be entering the drum 20 with steam from the forced circulation section of the generator. For example, if 110,000 pounds of feed water an hour is delivered to the economizer I3 for passage through the forced circulation section of the generator, furnace I8 will -be so operated that approximately 100,000 pounds per hour will be evaporated, and the remaining 10,000 pounds per hour will be delivered to the drum 20 and will be evaporated in the natural circulation section of the generator by suitable operation of furnace 24. With a constant water level in drum 20, water will always be present in the coils of the forced circulation section, so that all superheating will be effected in the superheater only.

The steam pressure and the degree of superheat is controlled by varying the relative rates of combustion in the furnaces I 8 and 24. Variations in the rate of firing of the natural circulation section furnace 24 will take care of or provide for, variations in load on the generator, While variations in the rate of firing of furnace I8 will provide control of superheat temperature and will also provide for variations in load in conjunction with the firing of furnace 24. For example, if it is desired to lower the degree of superheat, the rate of firing of furnace I8 will be decreased which will not only lower the steam temperature but will also reduce the rate of evaporation of water in the bank of tubes II. To compensate for this reduced evaporation, the rate of firing of furnace 24 is increased to the extent necessary to take care of the load and to maintain the level of water in the drum 20. Conversely, if it is desired to increase the degree of superheat, the rate of firing of furnace I8 is increased which will raise the steam temperature and will at the same time increase the rate of evaporation in tube bank I'I, to compensate for which the rate of firing of furnace 24 is reduced. In this manner, the steam temperature may be varied as desired with constant or variable load, or the temperature may be maintained constant or substantially so, over a wide load range. The rate of firing of the furnaces I8 and 24 may be accomplished by varying the intensity of firing of the steam flows into outlet header 29 and through 55 burners or by varying the number of burners in operation. The control of the burners and the feed pump I2 and the interrelationship of their individual operation is preferably eiected automatically, but such control may be effected manually.

Ordinarily, the total steam generating surface in the forced circulation section will be greater than the corresponding surface in the natural circulation section, andit may be disposed in any suitable vor desired position Without regard to gravitation. Circulating pumps are not required for the generator, nor is water injection into the superheater necessary. The Water now to the generator is controlled simply bythe Water llevel in the steam and Water drum'fl'although supplementary devices based on changes in steam demand or rise in temperature of the fluid ntering the steam drum may be '.used, if ,.desired.

The Water in either or both of the drums 20 and 22 of the natural circulation section may beblown down ,to reduce `the concentration of salts inthe generator.

It will be apparent that changes maybe made in the form, location and relative arrangement of the ,sei/.eral parts .of the generator and superheater disclosed kWithout departing from the principles of the invention. Hence, it will be understood that the invention is vnot to be limitd .excepting by the scope of the appended claims.

What is claimed is:

1. A vapor generator ,comprising va setting, a forced circulation vapor generating section in the setting, Ia natural circulation vapor generating section in the setting and into which vapor and liquid from the `forced circulation section is discharged to supply the liquid therefor, and independent means for iiring each section, the arrangement being such that the gases from each firing means flow in substantial heat exchange relationship with but one of said sections.

A,2. A vapor generator comprising a setting, a forced circulation vapor generating section in the setting, a .natural circulation Vaporgenerating section in the setting, a vapor and liquid drum common to both sections, independent means forring each section, the arrangement .beingsuch that the gases from each ring means ow in Vsubstantial heat exchange Vrelationship with but one of said sections, and a ,superheater having tubes in heat exchange relationship with .the `gases produced in iiring .the forced circulation section.

3. A vapor generator comprising a setting, a forced circulation vapor generating section in the setting, a natural circulation Vapor generating section in the setting comprising upper and lower drums and vapor generating tubes connecting the drums, the Vapor and liquid outlet of the forced circulation section being connected to said upper drum, and independent means for firing each section, the arrangement being such that the gases from each firing means flow in substantial heat exchange relationship with but one of said sections.

vA ,vapor generator comprising a setting, a fprced circulation vapor generating section in vthe lsetting.comprising a bank of vapor generating tubes, a furnace, and a feed pump for deliver'ing liquid to said tubes, a natural circula- 4tion `vapor generating ,section in the setting comprising upper and lower drums, vapor generating tubes connecting the drums, and a furnace, theyaporrand liquid outlet of the forced circulation .Section being connected to said upper drum, a superheater having tubes disposed in heatexchange relationship only with the gases produced in the furnace of the forced circulation section, and burners for liring each furnace, the arrangement being such that the gases from each iiring means flow in substantial heat exchange relationship with but one of said sections.

l5. A steam generator comprising a setting, a forced circulation steam generating section in the setting, a natural circulation steam generating section in the setting, `the arrangement being such that the forced circulation section discharges steam and water into the natural .circulation section, as uperheater in the forced circulation section, and one or more fuel burners for firing each section, the sections being disposed so that each is out of substantial heat exchange relationship with the gases produced by the burners for firing the other section.

6. A vapor generator comprising a setting, a forced circulation vapor generating section in the section, a natural circulation Vapor generating syecton in the setting and into which vapor and liquid from the Vforced circulation section vis discharged to supply the liquid therefor, a superheater in the forced circulation section, and independent means for firing each section, the arrangement being such that the gases from Aeach firing means flow in substantial heat exchange relationship With but one of said sections.

JOHN BLIZARD. 

